Mars is often referred to as a desert world, and for good reason – its surface is barren, dry and cold. While water was abundant in the distant past, it has long since disappeared from the surface, although ice, snow, frost and fog are still common. Other than liquid brines possibly trickling at times, all [...]

Fraser. I think extrapolating the result of a few soil samples from near the Phoenix lander into a global Martian climate for ~ 600 million years is a bit of a reach. Soils in Antarctica don't show weathering at the rate of the high Sierras either because of frozen trapped water there,too. As has been previously shown, the Fe-60 deposits in marine sediments on Earth indicate that the Earth received incoming deposits of supernovae ejecta from nearby supernovae during the last few million years...(as many as 6 separate events), not the last 600 million, and those events rained down water, carbon monoxide, olivines, pyroxenes, graphites, and other entrained dust particles often found in ejecta clouds. Each event could have contributed enough water for transitory lakes near the Martian equatorial latitudes, where even today daytime temperatures mapped from our orbiters show temperatures well above freezing in pockets. Where there's water on Earth, life has happened.